Production of metallic halides



Aug. 31, 1965 R. w. ANCRUM ETAL 03,881

PRODUCTION OF METALLIC HALIDES Filed Jan. 15, 1958 United States Patent3,203,881 PRODUCTIGN 'OF METALLIC HALIDES Robert William Ancrum,Saint-Germain-en-Laye, Paris,

France, and Arthur Wallace Evans, 'Nunthorpe, Middlesbrough, England,assignors to British Titan Products 'Company Limited, 'Billingham, Co.Durham, England, a corporation of the United Kingdom Filed Jan. 15,1958, Ser. No. 709,155 Claims priority, application Great Britain, July16, 1952, 17,971/52; Nov. 27, 1957, 37,034/57 7 Claims. (Cl. 204-611)This application is a continuation-in-part of application Serial No.366,611, filed July 7, 1953 Serial No. 700,638, filed December 4, 1957,both now forfeited, and Serial No. 700,556, filed December 4, 1957.

This invention comprises improvements in or relating to the productionof metallic halides, particularly the halides of tetravalent metals. Theexpression tetravalent metals is to be understood to include silicon.References herein to halides and halogenation are to be understood toexclude fluorides and fluorination.

The invention is more particularly concerned with the production of themetallic halides by an electrolytic process using as starting materialscorresponding metalliferous materials. In the electrolytic process themetallic halide is produced on the anode, which comprises themetalliferous material. The electrolyte serves as a source of halogenfor the halogenation of the metalliferous material, and is a metalhalide in a molten state, especially a halide of an alkali metal and/oran alkaline earth metal, suitable metal halides being lithium chloride,sodium chloride, potassium chloride, calcium chloride, strontiumchloride, barium chloride, beryllium chloride and magnesium chloride. Itwill be appreciated that the metal of the electrolyte is deposited onthe cathode of the electrolysis apparatus, and in some cases this is ofinterest as a method of producing such metal, especially for examplewhen a magnesium halide is used as the electrolyte, whereby magnesium isproduced on the cathode.

The invention is of particular importance in respect of the halogenationof siliceous materials, e.g. silica as such, and also compounds ofcombinations of silicon dioxide with other oxidic bodies, e.g. zirconand bauxitic clays or residues resulting from the extraction of thealuminium constituents from the latter. It will be understood howeverthat the invention applies also to the production of halides frommetalliferous materials other than siliceous materials, e.g. baddeleyitewhich consists mainly of zirconium dioxide.

The invention of application Serial No. 366,611 relates to a method or"preparing titanium tetrahalide which comprises electrolysing a fusedbath consisting of a member of the group consisting of alkali metalhalides and alkaline earth metal halides in which the halide componentis that of the titanium compound desired with an anode comprising amixture of carbon with a material containing at least 90 percent of TiOthe amount of carbon being at least stoichiometrically equivalent to theamount of "H0 present in said material, maintaining the temperature ofthe bath 700 to 1400 C., maintaining a neutral atmosphere over theelectrodes, whereby titanium tetrahalide is formed and vapourising andremoving the titanium tetrahalide from the bath.

The invention will now be described with particular reference to theproblems involved in the halogenation, especially chlorination, ofsiliceous materials, and especially silicon dioxide.

2 Silicon. tetrahalides, and especially silicon tetrachloride, arebecoming of increasing importance in commerce. They have economicadvantages, especially from the aspect of purification, i.e. on accountof their comparatively low boiling points and ease of distillation, andare of special interest as intermediates in the preparation of variouschemicals which may be silico-organic, or even in the preparation ofspecial forms of high grade silica, particularly in the preparation offine silica as described and claimed in application Serial No. 598,913filed July 19, 1956, now abandoned.

The chlorination of metal oxides, including oxides of metalloids such assilicon, has been the subject of considerable research 'over many yearsbut the chlorination of silica in particular has proved to be verydifiicult. For example Green, Richardson & Clews, Trans. Brit.

I Ceram Society, 41, 196, 1942, indicate the conditions for chlorinationof a number of oxides, and have demonstrated that silica is extremelydifiicult to chlorinate under normal conventional procedures, i.e., whenadmixed with an oxygen acceptor such as carbon. According toconventional practice a mixture of silica and carbon will onlychlorinate with difficulty at temperatures of the order of 1150 C. andfor efficient operation much higher temperatures would be required.

Similar problems have arisen in the chlorination of certain othersiliceous materials, for instance compounds of silicon dioxide, e.g.zircon, bauxitic clays, or residues following extraction of thealuminium constituents from the latter.

The production of silicon tetrachloride by chlorination of silica hasposed a serious problem economically. It will be obvious that there aredifficulties in respect of the design and construction of plant andparticularly in the selection of materials of construction, since, attemperatures of the order mentioned above, there are very few types ofcontainers which will withstand the action of chlorine, and which willbe sufficiently gas-tight to warrant their use, bearing in mindespecially the danger to health involved by gas-leaks. Thus in theproduction of silicon tetrahalides, and particularly in the productionof silicon tetrachloride, there is a long-felt want in respect of asuitable and commercially satisfactory method of production. 7

We have now developed a method of chlorinating silica and othersiliceous bodies such as zircon, by means of which chlorination can beeifected at relatively low temperatures, i.e. below 1200 C., at whichchlorination would otherwise be inoperable and the problems enumeratedabove can be overcome in respect of the construction of plant and ofeifecting economies in production.

Accordingly, there is provided, by an embodiment of the invention, amethod for the production of silicon tetrahalide, which method compriseselectrolysing a fused metal halide salt, using an anode comprising amixture of carbon and siliceous material, the halogen liberated at areso low as to be comparatively unimportant. When mixtures of halides areused, the properties of the mixtures as opposed to those of theindividual constituents are relevant. Into this bath is inserted theanode, which may be constructed in a variety of ways and which is moreparticularly described below, but which essentially comprises aconducting rod e.g. carbon on which is built or moulded, or which issurrounded or otherwise closely associated with, the mixture ofsiliceous material with an adequate proportion of carbon. The cathodeconsists of a conducting rod which maybe any of a group of materials,e.g. carbon, iron, tantalum and tungsten. In some instances, at least,tungsten is the preferred material for use as an electrode, e.g. whencalcium metal is deposited on a carbon cathode, it is found thatcarbides are liable to form. The electrodes in the bath are separated,at least in so far as the upper portion of the bath and the vapour spaceabove are concerned, i.e. there is a barrier between the two whichextends below the surface of the bath to a level to be determinedaccording to choice of one skilled in the art.

An important feature in the operation of this invention is theconstruction of the anode. This may be accomplished in a variety ofways, as is apparent when a selection of such procedures is described.The siliceous starting material may be a prepared substance, or anatural mineral such as quartz, cristobalite or tridymite, and may be asilicate such as zircon. The siliceous material may be used in asand-like form and mixed with carbon of a similar size, or the twostarting materials may be initially of somewhat large dimensions and besuitably comminuted together. The carbon employed may be selected from anumber of well-known sources, which may include charcoal and petroleumcoke or may even be derived in situ from carboniferous material, e.g.coal. The term carbon is to be understood to include graphite, amorphouscarbon and mixtures thereof. The siliciferous material and carbon,suitably mixed, may be for instance packed into a porous pot with acarbon rod inserted therein. Alternatively, the siliceous-carbon mixturewith the aid of a bonding agent such as gum, pitch or glue may becompressed, and if necessary fired, and an electrode, preferably ofcarbon, inserted into the compressed mass. In a further alternative, thecarbon and siliceous material may be made into a paste with glycerine ordehydrated castor oil with or without the presence of water, and thispaste may be shaped, dried and fired, preferably in a non-oxidisingatmosphere, with or without a core of carbon, at 900l400 C. to produce ahard electrically-conducting mass. A further method may consist ofpacking either the siliceous material 'or carbon in the form of looselumps into a porous pot with an electrode inserted therein, or incertain cases loosely packed lumps or compressed powder, as describedabove, may be inserted into a hollow porous electrode, from which thesilicon tetrahalide subsequently generated may be withdrawn. If it isdesired to make the process operate continuously, a mixture, preferablyof finely-divided siliceous material and carbon with or without abonding agent, may be fed in the form of a thick paste onto the topsurface of a slowly decaying anode which is periodically or continuouslylowered into the bath as it becomes eaten away; the paste so fed to theanode will, on account of the heat transmitted through the submergedpart of the anode, and the heat derived by convection and radiation fromthe anode chamber, dry, cake and ultimately bind and cement together inthe form of a hard adherent mass and so become suitable to function asan anode.

As has already been mentioned, the following salts are suitable for usein the bath, either separately or in admixture, lithium chloride, sodiumchloride, potassium chloride, calcium chloride, strontium chloride,barium chloride, beryllium chloride and magnesium chloride. These saltsshould be used in anhydrous form.

In operation of the process generally with respect to the simple type ofcell described above using calcium chloride as the metal halide saltbyway of example, the calcium chloride is heated to a temperature in theneighbourhood of 1000 C. The vapour space immediately above the liquidin both the anode and the cathode compartments is swept with an inertgas, so as to avoid the presence of reactive gases, such as oxygen. Theflow of such inert gases may then either be arrested for the duration ofthe electrolysis, or according to the discretion of the operator, may becontinued so as to assist in removing the product vapours generatedduring the electrolysis. The electrodes are connected to a source ofelectric energy and electrolysis ensues, the chlorine being liberated atthe anode, and immediately reacting with the mixture of siliceousmaterial and carbon so as to form silicon tetrachloride and acarbonaceous gas, e.g. carbon monoxide and/or carbon dioxide. Thesilicon tetrachloride and carbonaceous gas generated at the anode andappearing in the vapour space above the calcium chloride are led,assisted if necessary by a flow of inert gas, to a suitable condensingapparatus for the condensation of the silicon tetrachloride. Thecarbonaceous gas is then either discharged to the atmosphere, orutilised as desired. Simultaneously, at the cathode there is liberatedthe calcium, i.e. the metal corresponding to the fused salt of which thebath is composed.

Depending on the properties of the metal of which the salt is composedat the temperature under which the electrolysis takes place, the metalmay be deposited and collected at the cathode in a variety of ways. Themetal may, for instance, be deposited on the cathode in the form of asolid which may adhere to the cathode and be removed by periodic orcontinuous withdrawal of the cathode. Alternatively, the metal may bedeposited at the cathode and subsequently fall away again as a mud intothe cathode bath from which it may be removed by subsequent purging ofthe bath and extraction by wellknown means. The metal, if liquid at thetemperature of the bath, may be collected as a liquid pool which may beperiodically removed from the bottom or from the surface of the bath,depending on the relative densities of the metal and the fused salt. Themetal may be removed as such or in the form of a solution. Alternativelythe metal may be deposited onto a liquid cathode which again may beperiodically purged for the removal and refinement of the depositedmetal contained therein. On the other hand the metal deposited at thecathode may at the temperature of the bath be in the form of a vapour,which may be removed from the cathode compartment by suit able methods,including the assistance, if necessary, of inert gas flowingtherethrough, followed by condensation of the metal vapour, or any othertreatment which may be particularly applicable.

The invention is more particularly described with reference to theaccompanying diagrammatic drawing, which shows a view in elevation of anapparatus suitable for carrying out the process of the invention.

A container 1, which may consist of metal, for instance iron, or somesuitable ceramic, e.g. silica, is filled with a molten salt 2, in thisinstance magnesium chloride,

- to a level 3. The container is heated externally by consilica tube 9,the lower end 12 of which is left open and immersed in the bath, itsprecise position being variable, as desired. The carbon rod 21 isafiixed by means of a bung 10 through the top of the silica tube 9, anda lead 11 from the carbon rod 21 is connected to the positive pole ofthe DC. electric power supply. The silica tube 9 has a side conduit 13,which is positioned immediately above the level of salt 2 in the bath,and through which may be fed inert gas or any suitable carrier gas asdescribed below. According to requirements, this gas is discharged fromthe top of the silica tube 9 via a duct 14 to a condenser or otherequipment appropriate for removal of the silicon tetrahalide produced atthe anode.

In the operation of this apparatus, the bath is heated to about 1000C.,the anode and the cathode compartments are swept with inert gas, and thecurrent is passed through the cell so that, a has already beenexplained, electrolysis is established; the chlorine liberated at theanode reacts with the silicon dioxide and carbon to pro duce silicontetrachloride and carbonaceous gases which, assisted, if necessary, bycontinuing the flow of inert gas, are removed from the anode compartmentfor the silicon tetrachloride to be collected by condensation;simultaneously, magnesium, i.e. the metallic element of the halide saltused, is deposited at the cathode, and forms as a pool on the bottom ofthe salt bath, being removed by periodic purging. During the passage ofcurrent through the cell, heat is generated therein and this may augmentthe heating of the bath and may suffice to maintain it at the requiredtemperature. It will be obvious that this latter effect will depend inlarge measure on the dimensions of the cell and upon the construction,especially the degree of insulation provided.

The silicon tetrahalide formed may, if necessary or desirable, besubjected to suitable purification treatment, e.g. fractionaldistillation or any other known means, and may be used as anintermediate for the production of pigments, for instance by vapourphase reactions, either with steam or by direct oxidation, to yieldpigments of a very high degree of whiteness and with a controlledparticle size of the order of, for instance, 0001-0005;, such productshaving exceptional value in for instance the rubber industry. Thesilicon tetrahalides may also be used in connection with the productionof organic materials to produce the so-called silico-organic compounds,well known in the art.

The following examples are given for the purpose of illustrating theinvention; all parts and percentages are by weight.

The apparatus used in the examples comprises, with reference to thefigure illustrated in the accompanying drawing, a silica pot 1, of 4"diameter and 5" height into which is inserted a fused silica chamber 9,which is open at the bottom, and is sealed at the top by a plug with aA" diameter anode 21 passing through the plug and hav ing bonded on itslower end, i.e. that which is immersed within the bath, a moulded mass 8formed as follows:

Approximately one part of non-graphitising carbon, such as 82.4% C.Northumbrian coal or 83.1% C. Yorkshire coal or sugar charcoal, and twoparts of the siliceous material to be chlorinated, both constituentsground to pass a standard 200 mesh sieve, were intimately mixed withabout one tenth of a part of a gum, such as gum acacia, or gum arabic orgum tragacanth, and made into a stiff paste with a few drops ofdehydrated castor oil. This paste is moulded round the lower end of theanode 21 to form a rough cylinder approximately 4 in diameter and 2 /2"in length. The molded electrode is then placed in an atmosphere of coalgas and heated to 1000 C. for three hours. On removal, the electrode isready for use. The amount of carbon present in the fired electrode isabout by weight.

Also inserted in the bath to a depth of about 2 /2" is a cathode 5,which consists of a tungsten rod /8" in diameter.

Example 1 Using the apparatus described above, a melt of fused calciumchloride was prepared by external heating of the silica pot to atemperature of 1030 C., as measured by the thermocouple 4. The mouldedportion of the anode was made from a carbon/silica sand mixture bondedwith gum acacia. The atmosphere in contact with the top of the anode 11,i.e. in the chamber 9, was swept with inert gas by passing nitrogenthrough conduit 13 and discharging through 14. Thereafter the port 13was closed, and conduit 14 connected to a condensing and collectingsystem for the silicon tetrachloride and other product gases. The anodeand cathode were thereafter respectively connected to a DC. circuitwhich produced a voltage of 4.8 across the electrodes and a current of5.8 amps. This is equivalent to a current density of 15 amps./dm. at theanode, and of 75 amps./dm. at the cathode. With the bath maintained byexternal heating at a temperature of 1030 C., these conditions weremaintained for 3 /2 hours, during which period the gases, whichconsisted in the main of carbonaceous gas, silicon tetrachloride andsome chlorine which escaped attack at the anode, were removed via theport 14. In all, 10 litres of gas, as measured at room temperature, werecollected and were found to contain 1590 cc. of CO and 3900 cc. of CO.It was found that of the chlorine liberated had been converted tosilicon tetrachloride.

Example 2 The apparatus described above was again used, but the bathconsisted of magnesium chloride fused and maintained at a temperature of1025 C. The same procedure was followed, and, on connecting with the DC.current, the voltage across the electrodes was 4.2 and the current 6amps. The current density at the anode was 16 amps./dm. and the currentdensity at the cathode was 72 amps./dm. The operation was conducted for3 /2 hours and 10 litres of gas were collected. This gas, as measured atroom temperature, was found to contain 1480 cc. of CO and 3520 cc. ofCO, and 70% of the chlorine generated at the anode had been converted tosilicon tetrachloride.

Example 3 The apparatus and cathode were the same as above, but the meltconsisted of 50% sodium chloride and 50% potassium chloride maintainedat a temperature of 980 C. The moulded portion of the anode was preparedfrom a zircon sand/ carbon mixture. The voltage across the electrodeswas 4.5 and the current 6 amps, the currenty density at the anode being12 amps./dm. and at the cathode 70 amps./dm. The total volume of gascollected from the anode over a period of 2 hours was 10 litres, andthis was found to contain 420 cc. of CO and 2900 cc. CO. The conversionof chlorine liberated at the anode was 71%. The product gas containedboth silicon tetrachloride and zirconium tetrachloride, zirconiumtetrachloride being primary condensed before the silicon tetrachloride.

Example 4 The apparatus and cathode were the same as above, but themoulded portion of the anode was prepared from a carbon and groundsilica sand/ 10% ground zircon sand mixture. The bath consisted of fusedcalcium chloride maintained at a temperature of 960 C. The voltageacross the electrodes was 5.1 and the current 5.8 amps, the currentdensities being 14 amps./dm. for the anode and 72 amps./dm. for thecathode. The duration of the operation was 45 minutes, during which time5 litres of gas were collected, the gas containing 450 cc. of CO and 300cc. of CO. The conversion of chlorine liberated at the anode was 63%. Aswith the product obtained from Example 3, zirconium tetrachloride andsilicon tetrachloride were obtained.

Example 5 The apparatus and the cathode were as described above, but themoulded portion of the anode was prepared from a carbon/spent bauxiticstone mixture. The spent bauxitic stone had a composition of 7.6% TiO6.7% A1 78.4% SiO 0.65% Fe. The bath consisted of fused magnesiumchloride maintained at 1020 C. The voltage across the electrodes was 4.8and the current 5.9 amps, the current density at the anode being 12amps./ dmF, and the current density at the cathode being 70 amps./dm.The duration of operation was 3 hours, and the gas collected via theport 14 had a volume of 9 litres as measured at room temperature,containing 1010 cc. CO and 3370 cc. CO. Of the chlorine liberated at theanode, 69% was converted to silicon tetrachloride which was recovered bycondensation.

Although the invention has been more particularly described withrelation to the formation of silicontetrachloride, as has already beenmentioned the invention applies also to the halogenation of othermetalliferous materials to form the corresponding metallic halides. Whenforming a halide other than a chloride, the electrolyte will of coursecomprise the appropriate halide of a suitable metal. Whenusing otherstarting materials than have been particularly described above, thenecessary conditions of operation, e.g. the temperature, may be variedas desired for the particular material used. Generally the temperaturewill lie between 700 C. and 1400 C., preferably between 900 C. and 1100C.

Example 6 A graphite rod was covered with paste consisting of coal andTiO in dehydrated castor oil, and the whole was dried and fired. Theresulting electrode was inserted in a porous pot inside a cellcontaining a mixture of sodium and potassium chloride in equalquantities heated to 900 to 1000 C. The melt was electrolysed with ananode current density of 11 amps. per square decimeter and under theseconditions, titanium tetrachloride was formed at the anode.

Example 7 A molten bath was employed containing 50% potassium chlorideand 50% sodium chloride and maintained at 820 C., using an anodeprepared by mixing titanium oxide and coal and pre-fired in anon-oxidising atmosphere, and a cathode consisting of a carbon rod, theanode department being sealed to permit only the extraction of gases.The cell was operated with an anode density of amps. per squaredecirneter and at the anode titanium tetrachloride was liberated admixedwith carbon dioxide and some carbon monoxide, and the titaniumtetrachloride was subsequently recovered by condensation.

Example 8 The cell contained a molten mixture consisting of 50%potassium chloride and 50% sodium chloride. The anode comprised a rod ofsintered titanium carbide and the cathode was a carbon rod. The anodecompartment was sealed to permit only the extraction of gases.

With the cell maintained at 700 C. and an anode current density of 10amps. per square decimeter, titanium tetrachloride was liberated in theanode compartment and the titanium tetrachloride vapours were recoveredby condensation.

What is claimed is:

1. A process for producing silicon tetrachloride, comprisingelectrolysing a fused bath consisting of at least one member of thegroup consisting of alkali .metal chlorides and alkaline earth metalchlorides with an anode comprising a mixture of carbon and siliceousmaterial containing at least 90% by Weight of silicon dioxide, theamount of carbon being at least stoichimetrically equivalent to theamount of silicon dioxide present in the said siliceous material,maintaining a neutral atmosphere over the electrodes, preventing metalevolved at the cathode from contacting the products of the anode,maintaining the temperature of the bath at between 700 to 1400 C.whereby silicon tetrachloride is formed, and vapourising and removingthe silicon tetrachloride from the bath.

2. A process for producing silicon tetrahalide which compriseselectrolyzing a fused bath of at least one member of the groupconsisting of alkali metal halides and alkaline earth metal halides,said bath being substantially inert to the elemental halogen of saidhalide, with an anode comprising a mixture of silicon dioxide and carbonat a temperature of 700 to 1400 C., contacting the halogen liberatedfrom the bath pursuant to electroylsis with said mixture whilemaintaining the temperature of the bath at between 700 to 1400 C. andthereby producing silicon tetrahalide, and vaporizing and removing thesilicon tetrahalide from the bath.

3. A process for producing silicon tetrachloride which compriseselectrolyzing a fused bath of at least one member of the groupconsisting of alkali metal chlorides and alkaline earth metal chlorides,said bath being substantially inert to chlorine, with an anodecomprising a mixture of SiO and carbon at a temperature of 700 to 1400C., contacting the chlorine liberated from the bath pursuant to theelectrolysis with said SiO while maintaining the temperature of the bathat between 700 to 1400 C. and thereby producing silicon tetrachloride,and vaporizing and removing silicon tetrachloride from the bath whilepreventing the metal evolved at the cathode from contacting the evolvedsilicon tetrachloride.

4. The process of claim 3 wherein the anode comprises a mixture ofcarbon and silica sand, the amount of carbon being at leaststoichiometrically equivalent to the SiO of said sand.

5. A process for producing silicon tetrachloride which compriseselectrolyzing a fused bath of at least one member of the groupconsisting of alkali metal chlorides and alkaline earth metal chlorides,said bath being substantially inert to chlorine, with an anodecomprising a mixture of zircon and carbon at a temperature of 700 to1400 C., contacting the chlorine liberated from the bath pursuant to theelectrolysis with said zircon while maintaining the temperature of thebath at between 700 to 1400 C. and thereby producing silicontetrachloride, and vaporizing and removing silicon tetrachloride fromthe bath While preventing the metal evolved at the cathode fromcontacting the evolved silicon tetrachloride.

6. A process for producing a volatile halide of a tetravalent metal fromthe group consisting of silicon and zirconium which compriseselectrolyzing a fused bath of at least one member of the groupconsisting of alkali metal halide and alkaline earth metal halide, saidbath being substantially inert to said metal halide, with an anodecomprising a mixture of carbon and an oxide of a tetravalent metal ofthe group consisting of silicon and zirconium, contacting halogenliberated from the bath pursuant to the electrolysis with saidtetravalent metal oxide while maintaining temperature of the bath atbetween 700 C. to 1400 C. and thereby producing volatile metal halide,and vaporizing and removing metal halide from the bath while preventingthe metal evolved at the cathode from the contacting the evolved metalhalide vapor.

7. A process for producing a volatile halide of a tetravalent metalwhich comprises electrolyzing a fused bath of at least one member of thegroup consisting of alkali metal halide and alkaline earth metal halide,said bath being substantially inert to said metal halide, with an Ianode comprising a mixture of carbon and zircon, contacting the halogenliberated from the bath pursuant to the electrolysis with said mixturewhile maintaining the temperature of the bath at between 700 C to 1400C. and thereby producing volatile metal halide, and vaporizing andremoving tetravalent metal halide from the FOREIGN PATENTS bath Whilepreventing the metal evolved at the cathode 1 134 073 11/56 France fromcontacting the evolved metal halide vapor. 4/50 Great Britain ReferencesCited by the Examiner 5 gfig 5 23 UNITED STATES PATENTS 5 231 9 9Blackman 2o4 1 WINSTON A. DOUGLAS, Primary Examiner.

2,734,855 2/56 Buck et a1. 20461 JOHN R. SPECK, Examiner. 2,870,071 1/59Juda et a1. 20461

6. A PROCESS FOR PRODUCING A VOLATILE HALIDE OF A TETRAVALENT METAL FROMTHE GROUP CONSISTING OF SILICON AND ZIRCONIUM WHICH COMPRISESELECTROLYZING A FUSED BATH OF AT LEAST ONE MEMBER OF THE GROUPCONSISTING OF SILICON AND ZIRCONIUM WHICH COMPRISES ELECTROLYZING AFUSED BATH OF AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF ALKALIMETAL HALIDE AND ALKALINE EARTH METAL HALIDE, SAID BATH BEINGSUBSTANTIALLY INERT TO SAID METAL HALIDE, WITH AN ANODE COMPRISING AMIXTURE OF CARBON AND AN OXIDE OF A TETRAVALENT METAL OF THE GROUPCONSISTING OF SILICON AND ZIRCONIUM, CONTACTING HALOGEN LIBERATED FROMTHE BATH PURSUANT TO THE ELECTROLYSIS WITH SAID TETRAVALENT METAL OXIDEWHILE MAINTAINING TEMPERATURE OF THE BATH AT BETWEEN 700*C. TO 1400*C.AND THEREBY PRODUCING VOLATILE METAL HALIDE, AND VAPORIZING AND REMOVINGMETAL HALIDE FROM THE BATH WHILE PREVENTING THE METAL EVOLVED AT THECATHODE FROM THE CONTACTING THE EVOLVED METAL HALIDE VAPOR.